Controls on blowout evolution in southern Portugal: A 49-year analysis

Area of Science:

• Coastal geomorphology
• Dune dynamics
• Ecogeomorphology

Background:

• Blowouts are wind-formed depressions crucial for coastal dune sediment budgets and biodiversity.
• The drivers and temporal scales of blowout genesis, development, and decay are not well understood.

Purpose of the Study:

• To analyze the morphometric changes of blowouts over time.
• To identify the drivers and temporal scales of blowout evolution phases.
• To inform dune management strategies.

Main Methods:

• Digitized morphometric characteristics of blowouts from 1972-2021 imagery.
• Analyzed changes in blowout number, area, and shape over time.
• Correlated morphometric data with metocean and human activity time series.

Main Results:

• Blowout genesis phase (1-2 years) driven by physical factors and dune irregularities.
• Ongoing development phase shows expansion and rotation influenced by wind and internal factors.
• Natural decay phases were not observed; artificial sealing lasted 4 years.
• Reactivation occurred due to storm impacts on sealed blowouts.

Conclusions:

• A complete natural blowout cycle may exceed 50 years, driven by complex ecogeomorphic feedbacks.
• Natural evolution, rather than artificial sealing, is recommended for dune management.
• Storms can reactivate artificially stabilized blowouts.